This invention relates to autoclavable flexible tubing suitable for use with medical solution packaging.
Currently, it is common medical practice to package liquids such as medical solutions for parenteral administration in disposable, flexible pouches. These pouches should be characterized by collapsibility, transparency, and adequate mechanical strength. They must also be able to resist the relatively high temperatures required for heat sterilization of their contents, for example in an autoclave. Typically, medical solutions and the like are autoclaved at about 253xc2x0 F. for periods of 15 to 30 minutes.
Connector tubing is used in combination with such flexible pouches. This tubing is used to introduce additional materials to the medical solution inside the pouch, and to administer the medical solution to the patient. This connector tubing must be chemically and physically compatible with the medical solution pouch material. The tubing must also be resistant to the heat generated during autoclaving of the medical solution pouch and tubing. When the tubing is used in combination with for example a polycarbonate connector, it sometimes must be sealable to the connector material by means of ultrasonic, radio frequency (RF) or heat sealing. In some cases, a pin heater is inserted into the tubing to heat the inside as well as the outside of the tubing. It is especially required of such tubing that it be flexible without embrittlement or cracking of the tubing. In this regard, it is known that polyvinyl chloride for example becomes brittle at relatively low temperatures.
Of interest is U. S. Pat. No. 4,643,926 issued to Mueller and assigned to a common assignee with the present application. In the ""926 patent, a flexible film suitable for medical solution pouches is disclosed. This film may include a sealant layer of ethylene propylene copolymer, modified ethylene propylene copolymer or flexible copolyester; at least one interior layer of a polymeric material which imparts flexibility to the film, such as very low density polyethylene, ethylene propylene monomer blended with ethylene vinyl acetate copolymer, modified ethylene propylene copolymer, ethylene methyl acrylate copolymer, and modified ethylene vinyl acetate copolymer; and an outer layer of copolyester or ethylene propylene copolymer.
Also of interest is U.S. Pat. No. 4,948,643 issued to Mueller and assigned to a common assignee with the present application. The ""643 patent discloses a flexible medical solution tubing having an outer layer of e.g. modified EPC, an intermediate layer of e.g. a blend of modified EMA and EVA or VLDPE, and an inner layer of e.g. PVC, or a blend of copolyester and EVA.
It is an object of the present invention to provide a tubing suitable for use with medical solution packaging, the tubing having good flexibility.
Another object of the present invention is to provide a tubing suitable for use with medical solution packaging characterized by compatibility with prior art packaging and ability to withstand autoclaving of the tubing.
The term xe2x80x9cflexiblexe2x80x9d is used herein to define specific polymeric materials as well as characteristics of a resulting tubing whereby improved flexibility and/or bendability is obtained by the use of these specific polymeric materials. Flexible materials may be characterized by a modulus of preferably less than 50,000 PSI (ASTM D-882-81) and more preferably less than 40,000 PSI (ASTM D-882-81).
The term xe2x80x9cpolymerxe2x80x9d, xe2x80x9cpolymericxe2x80x9d, and the like, unless specifically defined or otherwise limited, generally includes homopolymers, copolymers and terpolymers and blends and modifications thereof.
The term xe2x80x9cethylene n-butyl acrylate copolymerxe2x80x9d or xe2x80x9cEnBAxe2x80x9d is used herein to refer to a copolymer formed of ethylene and n-butyl acrylate comonomer wherein the ethylene units are present as more than half of the total copolymer.
The term xe2x80x9cintermediatexe2x80x9d is used herein to refer to a layer of a multilayer tubing which is bonded on both of its major surfaces to another layer.
The terms xe2x80x9cmelt flowxe2x80x9d, xe2x80x9cmelt indexxe2x80x9d, xe2x80x9cMIxe2x80x9d, and the like are used herein to mean the amount, in grams, of a thermoplastic resin which can be forced through a given orifice under a specified pressure and temperature within 10 minutes. The value should be determined in accordance with ASTM D 1238-79.
The term xe2x80x9cethylene propylene rubberxe2x80x9d or EPR is used herein to define a polymeric elastomer obtained by the stereospecific copolymerization of ethylene and propylene, or the two of them with a third monomer such as diene (EPDM). Densities are typically below about 0.88 gm/cc as measured by ASTM D-1505.
The term xe2x80x9cethylene vinyl acetate copolymerxe2x80x9d (EVA) is used herein to refer to a copolymer formed from ethylene and vinyl acetate monomers wherein the ethylene derived units in the copolymer are present in major amounts and the vinyl acetate derived units in the copolymer are present in minor amounts.
The term xe2x80x9cethylene propylene copolymerxe2x80x9d is used herein to refer to a copolymer formed from polypropylene monomer and minor amounts, usually less than 6%, of ethylene.
The terms xe2x80x9ccopolyesterxe2x80x9d and xe2x80x9celastomeric copolyesterxe2x80x9d (EPET) and the like refer to polyesters synthesized from more than one diol and a dibasic acid. Copolyesters as used herein may also be characterized as copolymers of polyether and polyethylene terephthalate. More preferably copolyesters as used herein may be characterized as polymeric materials derived from 1,4 cyclohexane dimethanol, 1,4 cyclohexane dicarboxylic acid, and polytetramethylene glycol ether, or equivalents of any of the above, as reactants.
The term xe2x80x9cmodifiedxe2x80x9d and the like is used herein to refer to a polymeric material in which some or all of the substituents are replaced or supplemented by other materials or substituents, providing a change in properties such as improved flexibility or elastomeric properties. For example, a modified ethylene propylene copolymer is for example an ethylene propylene copolymer to which an elastomeric material such as Kraton(trademark) rubber has been added by any means.
The term xe2x80x9cpolymeric elastomerxe2x80x9d is used herein to refer to elastomeric styrene copolymers, EPR, or blends thereof.
A polymeric tubing comprises an intermediate layer comprising a polymeric elastomer, a blend of a low melt index EVA and a high melt index EVA, EnBA, or blends thereof; an inner layer, bonded to an inner surface of the intermediate layer, comprising a polymeric material selected from EVA, a blend of a low melt index EVA and a high melt index EVA, EMA, EnBA, or blends thereof; and an outer layer, bonded to an outer surface of the intermediate layer, comprising a polymeric material selected from polypropylene, ethylene propylene copolymer, and modified ethylene propylene copolymer.
In another aspect, a polymeric tubing comprises an intermediate layer comprising a blend of an EVA-based polymeric adhesive and an elastomeric copolyester; an inner layer, bonded to an inner surface of the intermediate layer, comprising polyvinyl chloride; and an outer layer, bonded to an outer surface of the intermediate layer, comprising a polymeric material selected from polypropylene, ethylene propylene copolymer, and modified ethylene propylene copolymer.